The present invention relates to a single station type ionization smoke sensor consisting of an ionization-type smoke sensor, a fire alarming device and a battery-replacement alarming device, which are accommodated in a single housing and which work with one or two normal dry batteries, and particularly to a single station type ionization smoke sensor which is capable of performing these three functions using a power-supply battery which produces a voltage smaller than the voltage required for widely available ionization-type smoke sensors.
A conventional battery-powered smoke sensor has been disclosed, for example, in U.S. Pat. No. 4,030,086, having three functions such as detection of combustion, generation of a fire alarm, and generation of an alarm for indicating that the battery is depleted. The smoke sensor disclosed in this U.S. patent is powered by a Mallory Battery, Model No. 304116 having an initial voltage of 12.3 volts, which voltage decreases to 10.6 volts when 60% of its power is consumed. The ionization-type sensors for detecting combustion are usually supplied with a voltage higher than 9 volts. In order to drive such a conventional ionization-type smoke sensor using normal dry batteries having an initial voltage of 1.5 volts, it is necessary to use six or more such batteries occupying a space which can not be accommodated in a housing of the usually employed size.